Grounding switchgears are conventionally incorporated into gas-insulated switching devices to ground main circuits during inspection of the devices. As disclosed in Patent Literature 1, when the main circuit is to be grounded, a movable contact on a grounding side is moved into contact with a stationary contact disposed on a main circuit side. Before the movable contact contacts the stationary contact, the main circuit should be disconnected to thereby apply no voltage to the stationary contact.